1. Field of the Invention
The present invention relates to position detecting apparatuses and library apparatuses and, more particularly, to a position detecting apparatus and a library apparatus that have a flag and a sensor for detecting the flag.
As is generally known, there is a magnetic tape apparatus using a magnetic tape as a recording medium among external storages of a computer. The majority of magnetic tape apparatuses use a magnetic tape cartridge having a tape 0.5 inches in width therein, wherein the tape is automatically fetched from a reel therein to load data. A magnetic tape library apparatus (hereinafter called a library apparatus) accommodates as many magnetic tape cartridges as necessary (entry), which are loaded into a magnetic tape recording-playing apparatus to write and read data.
The library apparatus includes a cabinet having a plurality of cells to accommodate magnetic tape cartridges, a magnetic tape recording-playing apparatus for recording and playing data, and a carrying apparatus for carrying the magnetic tape cartridges between the cabinet and the magnetic tape recording-playing apparatus.
A large-scale library apparatus is formed by connecting mutually a plurality of independent frames each of which accommodates a cabinet, a magnetic tape recording-playing apparatus or the like. Consequently, when such a large-scale library is assembled, there arises an increasing error with respect to alignment of individual parts constituting the large-scale library apparatus, whereby it becomes difficult to position accurately a carrying apparatus for each cell in a cabinet by using only estimated values regarding the architecture of the library apparatus obtained at the designing phase. Thus, in the library apparatus, there is provided a position detecting apparatus for detecting a position of the carrying apparatus relative to the cabinet or the magnetic tape recording-playing apparatus so as to correct misalignment.
2. Description of the Related Art
FIG. 1 shows an example of a conventional position detecting apparatus provided in a library apparatus 1. In FIG. 1, there is positioned a carrying apparatus so as to face a cabinet 3. In the carrying apparatus 2, there are provided a medium holding mechanism 5 and a sensor 7 on a base 6. A magnetic tape cartridge 4 is accommodated in a medium slot 14 provided in the cabinet 3. In addition, a flag 10 is provided at a predetermined position in the cabinet 3. A position detecting apparatus, which is operable to position the carrying apparatus 2 and the cabinet 3, comprises the sensor 7 provided in the carrying apparatus 2 and the flag 10 provided in the cabinet 3.
The carrying apparatus 2 is formed so as to move in any of X, Y and Z directions, represented by arrows in FIG. 1. The medium holding mechanism 5 has holding arms 8 for holding the magnetic tape cartridge 4. Thus, the carrying apparatus 2 can insert/eject the magnetic tape cartridge 4 into/from the cabinet 3.
The magnetic tape cartridge 4 ejected from the cabinet 3 is carried to a magnetic tape recording-playing apparatus not illustrated in FIG. 1 and is mounted thereon to record or play data. Also in the magnetic tape recording-playing apparatus, there is provided a flag 10 similar to that provided in the cabinet 3.
The flag 10 is accurately positioned relative to the medium slot 14 provided in the cabinet 3. As a result, the carrying apparatus 2 detects the flag 10 by using the sensor 7, whereby it becomes possible to position the medium holding mechanism 5 and the magnetic tape cartridge 4 (the medium slot 14).
FIG. 2 shows a structure of the conventional flag 10. As is shown in FIG. 2, the flag 10 comprises a black part 11 and a white part 12. Since the sensor 7 provided in the carrying apparatus 2 is a reflective sensor, the sensor 7 becomes OFF when the sensor 7 faces the black part 11 and ON when the sensor 7 faces the white part 12.
The flag 10 is square-shaped as a whole. The black part 11 is formed as a slightly smaller square than the flag 10. On the other hand, as is shown in FIG. 2, the white part 12 is located in an upper and left area of the black part 11 and is provided so as to form an inverse L-shaped area.
A description will now be given of a conventional process for detecting a relative position of the carrying apparatus 2 to the cabinet 3 by using the flag 10 shown in FIG. 2.
At the beginning, the carrying apparatus 2 is moved and positioned so that the sensor 7 can face a center P0 (hereinafter referred to as a nominal sensor position) of the black part 11 formed in the flag 10. Additionally, in the carrying apparatus 2, there is provided an encoder capable of detecting moving distances in the X, Y and Z directions, thereby detecting the moving distances of the carrying apparatus 2.
However, since there are some shape errors in individual parts constituting the carrying apparatus 2 and the cabinet 3 and there arises some unevenness at the assembling of the parts, a sensor detecting position of the sensor 7 cannot always be adjusted correctly to the nominal position P0 (the center in the black part 11 of the flag 10). Thus, even if the carrying apparatus 2 is moved to a predetermined position for the cabinet 3, there arises, in fact, misalignment between the carrying apparatus 2 and the cabinet 3.
This misalignment is equivalent to misalignment between the holding arms 8 and the magnetic tape cartridge 4. Accordingly, when the holding arms 8 attempt to hold the magnetic tape cartridge 4 while the misalignment remains, the holding arms 8 are in risk of not holding the magnetic tape cartridge 4 properly.
A description will now be given, with reference to FIGS. 3 through 5, of a holding operation of the medium holding mechanism 5 for the magnetic tape cartridge 4. In the description to be mentioned later, two coordinate systems of the magnetic tape cartridge 4 accommodated in the cabinet 3 and of the medium holding mechanism provided in the carrying apparatus 2 are set separately for the convenience of explanation. Then, the coordinate system of the magnetic tape cartridge 4 is represented as an Xxe2x80x2-Yxe2x80x2 coordinate, and the coordinate system of the medium holding mechanism 5 is represented as an X-Y coordinate.
FIG. 3 shows an ideal situation in which there is no shape error in individual parts constituting the carrying apparatus 2 and the cabinet 3 and there arises no unevenness at the assembling of the parts. In this situation, the Xxe2x80x2-Yxe2x80x2 coordinate of the magnetic tape cartridge 4 is consistent with the X-Y coordinate of the medium holding mechanism 5. As a result, the holding arms 8 can hold the magnetic tape cartridge 4 properly.
Here, in the magnetic tape cartridge 4, there is provided a receiving part 13 (a concave part similar to a receiving part 41 shown in FIG. 10) to embed the holding arms 8 therein. As a result, when holding the magnetic tape cartridge 4, the holding arms 8 interlock the receiving part 13.
FIGS. 4 and 5 show situations in which there arises misalignment between the carrying apparatus 2 and the cabinet 3. In the misalignment shown in FIG. 4, since the center P0 (the nominal sensor position) of the Xxe2x80x2-Yxe2x80x2 coordinate of the magnetic tape cartridge 4 coincides with a center P1 (hereinafter, called an actual sensor detecting position P1) of the X-Y coordinate of the medium holding mechanism 5, it is concluded that the misalignment is caused by the fact that one coordinate has rotated relatively to the other on the centers P0 and P1.
Regarding misalignment in a rotational direction as shown in FIG. 4, if the misalignment mainly results from slight defects such as the shape errors on individual parts constituting the carrying apparatus 2 and the cabinet 3 and the unevenness at the assembling of the parts, the relative position of the holding arms 8 to the receiving part 13 remains comparatively accurate. Consequently, even if the misalignment in the rotational direction occurs, the holding arms 8 can still hold the magnetic tape cartridge 4 properly.
On the other hand, in the misalignment shown in FIG. 5, the nominal sensor position P0 representing the center of the Xxe2x80x2-Yxe2x80x2 coordinate for the magnetic tape cartridge 4 does not coincide with the actual sensor detecting position P1 of the sensor 7 representing the center of the X-Y coordinate for the medium holding mechanism 5. In this situation, even if the misalignment in the rotational direction has the same extent as the misalignment shown in FIG. 4, there is a possibility that the holding arms 8 cannot interlock the receiving part 13 properly. Thus, it is likely that the magnetic tape cartridge 4 cannot be inserted and ejected for the cabinet 3 appropriately.
Accordingly, in the case in which the nominal sensor position P0 representing the center of the Xxe2x80x2-Yxe2x80x2 coordinate for the magnetic tape cartridge 4 does not coincide with the actual sensor detecting position P1 of the sensor 7 representing the center of the X-Y coordinate for the medium holding mechanism 5, it is necessary to detect a quantity of misalignment between the nominal sensor position P0 and the actual sensor detecting position P1 of the sensor 7 and use the quantity to correctly position the holding arms 8 and the magnetic tape cartridge 4 correctly. Thus, in the library apparatus, there is provided a position detecting apparatus having the sensor 7 and the flag 10.
A description will now be given of a conventional method of how the position detecting apparatus actually detects a quantity of misalignment between the nominal sensor position P0 and the actual sensor detecting position P1 where the sensor 7 is actually located. Here, the amount of misalignment in the X and the Y directions between the nominal sensor position P0 and the actual sensor detecting position P1 are represented by a xcex94X and a xcex94Y, respectively.
In the case in which the nominal sensor position P0 does not coincide with the actual sensor detecting position P1, as is shown in FIG. 2, the carrying apparatus 2 is moved in the Y direction until the sensor 7 becomes ON. At this time, an encoder measures a moving distance A of the medium holding mechanism 5.
After the above process is completed, the medium holding mechanism 5, in turn, is moved in the X direction until the sensor 7 becomes ON. At this time, the encoder measures a moving distance B of the medium holding mechanism 5.
The quantity of misalignment (xcex94X, xcex94Y) between the nominal sensor position P0 and the actual sensor detecting position P1 is computed by subtracting quantities a in the Y direction and b in the X direction between the nominal sensor position P0 and the white part 12 from the distances A and B as measured in the above manner, respectively. The quantities xcex94X and xcex94Y are used as correction values to correctly position the cabinet 3. In the above manner, even if there are some shape errors on individual parts constituting the carrying apparatus 2 and the cabinet 3 and there arises unevenness at the assembling of the parts, the carrying apparatus 2 (the medium holding mechanism 5) can insert/eject the magnetic tape cartridge 4 into/from the cabinet 3 and the magnetic tape recording-playing apparatus with high accuracy.
However, under the conventional position detecting apparatus, it is necessary to move the carrying apparatus 2 (the medium holding mechanism 5) in the Y direction and thereafter in the X direction to detect the misalignment quantities (xcex94X, xcex94Y) between the nominal sensor position P0 and the actual sensor detecting position P1. Consequently, there is a problem in that it takes a long time to detect the misalignment quantities (xcex94X, xcex94Y) due to the conventional detecting process requiring the carrying apparatus 2 be moved in the two directions.
The flag 10 is provided not only in the cabinet 3 but also in the magnetic tape recording-playing apparatus. In addition, in a case in which the flag 10 is provided in the cabinet 3 and the magnetic tape recording-playing apparatus, the flag 10 is conventionally provided at a plurality of positions in the cabinet 3 and the magnetic tape recording-playing apparatus rather than at only one position so as to enhance the accuracy of position detection.
Therefore, especially in a large-scale library apparatus having a large number of flags 10 therein, there arises a problem in that the resulting increasing number of operations influences the operating life of the carrying apparatus 2.
It is a general object of the present invention to provide an improved and useful position detecting apparatus and an improved and useful library apparatus in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a position detecting apparatus and a library apparatus that can spend less time performing a position detecting process.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a position detecting apparatus for detecting a relative position of a measuring member to a measured member, comprising: a flag provided in the measured member, the flag including a first area having first optical characteristics and a second area having second optical characteristics different from the first optical characteristics; a sensor detecting optically the first area and the second area of the flag and further detecting a relative position, wherein the first area is formed as a pair of triangles or trapezoids that are positioned symmetrically with respect to an axis of the flag, and the sensor is adapted to detect the flag linearly, and wherein the position detecting apparatus is adapted to detect the relative position of the measuring member to the measured member based on a coordinate of a boundary position between the first area and the second area in a linear track detected by the sensor.
According to the above-mentioned invention, the sensor detects linearly the first area formed as a pair of triangles or trapezoids being positioned symmetrically with respect to an axis. Based on this detection result, the sensor detects a relative position of the measuring member to the measured member. At such time, the sensor uses some geometrical characteristics regarding the pair of triangles and trapezoids and the alignment with the axis to perform the position detecting process efficiently.
In fact, the sensor can detect easily the relative position of the measuring member to the measured member by using a coordinate of an intersection of a detecting line by the sensor and the first area. Also, the sensor can detect successfully the relative position even if the sensor performs the position detecting process only in one direction by using the geometrical characteristics, thereby shortening the time required to perform the position detecting process.
Also, the sensor finds a coordinate of a boundary between the first and the second areas, thereby performing a computation for the position detecting process. By using the geometrical characteristics, the position detecting process can be performed through a simple and time-saving computation.
In the above-mentioned position detecting apparatus, the sensor may be formed of a line type solid-state image sensing device.
According to the above-mentioned invention, when the line type solid-state image sensing device is used as the sensor, it is possible to detect a length of the sensor collectively, thereby spending less time performing the position detecting process than a scanning type sensor.
Additionally, there is provided according to another aspect of the present invention a library apparatus comprising: a medium storage cabinet storing a medium; a recording-playing unit performing a recording-playing process on the medium; a carrying mechanism carrying the medium between the medium storage cabinet and the recording-playing unit; and a position detecting apparatus for detecting a relative position of a measuring member to a measured member, comprising: a flag provided in the measured member, the flag including a first area having first optical characteristics and a second area having second optical characteristics different from the first optical characteristics; a sensor detecting optically the first area and the second area of the flag and further detecting a relative position, wherein the first area is formed as a pair of triangles or trapezoids that are positioned symmetrically with respect to an axis of the flag, and the sensor is adapted to detect the flag linearly, and wherein the position detecting apparatus is adapted to detect the relative position of the measuring member to the measured member based on a coordinate of a boundary position between the first area and the second area in a linear track detected by the sensor, wherein the flag is provided either in the medium storage cabinet or the recording-playing unit, and the sensor is provided in the carrying mechanism.
According to the above-mentioned invention, if the flag constituting the position detecting apparatus is provided either in the medium storage cabinet or the recording-playing unit and the sensor is provided in the.carrying mechanism, it becomes possible to insert and eject the medium for the medium storage cabinet with high accuracy when the carrying mechanism carries, inserts and ejects the medium for the medium storage cabinet.
In the above-mentioned library apparatus, the sensor may be provided in a neighborhood of a medium holding mechanism for holding the medium carried by the carrying mechanism.
According to the above-mentioned invention, since there is provided a sensor in a neighborhood of a medium holding mechanism for holding the medium carried by the carrying mechanism, it becomes possible to enhance accuracy of the position detection.
Additionally, there is provided according to another aspect of the present invention a library apparatus comprising: a plurality of medium storage parts in which a medium is stored, inserted and ejected; a carrying mechanism carrying the medium among the medium storage parts; a mark part providing a mark at a fixed position of the medium storage parts for detecting alignment of the medium storage parts; a sensor provided in the carrying mechanism and detecting the mark by scanning linearly; and a control part detecting an amount of misalignment from a normal position of the mark and controlling a carrying position of the carrying mechanism, wherein the mark detected by the sensor is defined by two boundaries, the boundaries being positioned symmetrically with respect to an axis of the mark part in a direction orthogonal with respect to a scanning direction of the sensor so that distances regarding the two boundaries vary continuously so as to detect the distances at a position different from an orthogonal direction with the scanning direction of the sensor, and wherein the control part detects the amount of misalignment from the normal position of the mark and controls the carrying position of the carrying mechanism based on the distances regarding the two boundaries.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.